Tempeh is a
fermented food typically made from soybeans, most
popular in Indonesia and other parts of Southeast Asia.
Tempeh is similar to tofu in providing a way to improve
the digestibility of soybeans, but different from it in
nutritional characteristics and eating qualities, as
tempeh's fermentation process and its retention of the
whole bean give it a higher content of dietary fiber and
vitamins, as well as firmer texture and stronger flavor.
Tempeh is used worldwide in the vegetarian cuisine as a
meat analogue.

Fermentation
Tempeh
begins with whole soybeans, which are softened and
cracked or pulped, then partly cooked. A mild acidulent,
usually vinegar, may be added and a culture containing
the fungus Rhizopus oligosporus is then mixed in. The
beans are spread into a thin layer and are allowed to
ferment for approximately 24 hours at a temperature
around 30?C (86?F). In good tempeh, the beans are knit
together by a mat of white mycelia. Under conditions of
lower temperature, or higher ventilation, gray or black
patches of spores may form on the surface -- this is not
harmful, and should not affect the flavor or quality of
the tempeh. This sporulation is normal on fully mature
tempeh. A mild ammonia smell may accompany good tempeh
as it ferments, but it should not be
overpowering.

Nutrition
The soy protein
in tempeh becomes more digestible as a result of the
fermentation process. In particular, the
oligosaccharides that are associated with gas and
indigestion are greatly reduced by the Rhizopus culture.
In traditional tempeh making shops, the starter culture
often contains other beneficial bacteria that produce
vitamins (like vitamin B12). In western countries, it is
more common to use a pure culture containing only
Rhizopus oligosporus. Because tempeh is made from whole
beans, it is also a good source of dietary
fiber.

Variations
Specialty tempehs may
be made from other types of beans, or may include a
mixture of beans and whole grains. In Indonesia, ripe
tempeh (two or more days old) is considered a delicacy.
Tempeh bongkrek is a variety of tempeh from Central
Java, notably Banyumas regency, that is prepared with
coconut. This type of tempeh occasionally gets
contaminated with the bacterium Burkholderia cocovenans,
and the unwanted organism produces toxins (Bongkrek acid
and toxoflavin) from the coconut, besides killing off
the Rhizopus fungus due to the antibiotic activity of
bongkrek acid. Fatalities from contaminated tempeh
bongkrek were once common in the area where it was
produced. Thus, the sale of tempeh bongkrek is
prohibited by law nowadays; clandestine manufacture
continues however due to the superior culinary value.
The problem of contamination is not encountered with
bean or grain tempeh, which have a different composition
of fatty acids that is not favorable for the growth of
B. cocovenans but encourages growth of Rhizopus instead.
When bean or grain tempeh has the proper color, texture
and smell, it is a very strong indication that the
product is safe. Tempeh bongkrek which is yellow is
always highly toxic due to toxoflavin, but tempeh
bongkrek with a normal coloration may still contain
lethal amounts of bongkrek
acid.

Preparation
In the kitchen,
tempeh is often prepared by cutting it into pieces,
soaking in brine or salty sauce, and then frying. Cooked
tempeh can be eaten alone, or used in chili, soups and
stews. Tempeh has a complex flavor that has been
described as nutty, meaty, and mushroom-like. Tempeh
freezes well, and is now available in many western
countries in ethnic markets and health food
stores.